With the general availability of high quality color reproduction, distinguishing an original from a copy and verifying, for example, a signature, on the original has become more difficult. More specifically, digital printers, scanners, and image editing software have made it possible for copies of legitimate documents to be made that are difficult to distinguish from the original.
One conventional approach to authenticating documents is the use of machine readable encoded data which is rendered onto a document or other physical media along with other information.
For example, authenticating information can be encoded into thousands of tiny, individual glyph elements. Each element consists of a small 45 degree diagonal line, as short as 1/100th of an inch or less, depending on the resolution of the printing and scanning that is used. Each glyph represents either binary 0 or binary 1, depending on whether the glyph slopes to the left or right. Sequences of glyphs can be used to encode numeric, textual, or other information. The glyphs are grouped together on the page, where the glyphs form unobtrusive, evenly textured gray areas, similar to a half-toned picture.
Another conventional approach to the problem of verifying document authenticity is the use of authenticating information embedded in a print, for example, a seal or a date and time. The embedded authenticating information catches the light when the print is tilted and can be seen as an additional and separate image. Moreover, watermarks, conventionally, have also been used to authenticate a document.
These various conventional methods of verifying a document share the feature that it is very difficult to reproduce the authenticating feature of the original on a conventional copier or scanner. Therefore, a copy of the original can be distinguished from the original.
However, the conventional methods of verifying a document have drawbacks. For example, glyphs need a device to decode the authenticating information. Moreover, conventional watermarks need a proper source of light to discern the authenticating information. In these various conventional methods, outside intervention; e.g., from either a machine (optical reader) or a light source; is needed to detect or discern the authenticating information.
Therefore, it is desirable to provide a method that enables authentication of an original document without the utilization of outside intervention; e.g. from either a machine (optical reader) or a light source. Moreover, it is desirable to provide a method that enables authentication of an original document through tactile perception. Furthermore, it is desirable to provide a method that enables authentication of an original document through tactile perception while preventing the authenticating information of the original document from being reproduced using conventional scanners and printers.